Network Management Systems like the OpenView Network Node Manager product are designed to discover network topology (i.e., a list of all network node in a domain, their type, and their connections), monitor the health of each network node, and report problems to the network administrator. OpenView Network Node Manager (NNM) is a product distributed by Hewlett-Packard Company of Palo Alto, Calif.
The monitoring function of such a system is usually performed by a specialized computer program which periodically polls each network element and gathers data which is indicative of the network element's health. A monitor program typically runs on a single host. However, in distributed networks, monitors may run on various nodes in the network, with each monitor reporting its results to a centralized display.
Network discovery is performed periodically using Internet control message protocol (ICMP) polling (pings and mask requests), simple network management protocol (SNMP) polling and/or other diagnostic requests. In addition or as an alternative to these protocols Desktop Management Interface (DMI) or Windows Management Instrumentation (WMI) which is also referred to as WBEM can be used.
For example by means of SNMP polling a configuration check operation is performed on each node. By default this configuration check operation is performed once each day whereby this period is configurable. This way it is determined at periodic intervals if any relevant configuration information has changed since the last check. More technical detail of the internals of the NNM product is disclosed on (http://support.openview.hp.com/pdf/dev_ov_netmon96.pdf), the entirety of which is herein incorporated by reference.
Elements of the code for discovering the topology of a plurality of network elements and the code for periodically polling a plurality of network interfaces associated with the plurality of network elements are also disclosed in U.S. Pat. No. 5,185,860 of Wu entitled “Automatic Discovery of Network Elements, and in U.S. Pat. No. 5,276,789 of Besaw et al. entitled “Graphic Display of Network Topology”. Both of these patents are hereby incorporated by reference for all that they disclose.
A disadvantage of scheduled discovery which is performed by the NNM product is that the discovery procedure can negatively affect network performance when the discovery procedure is carried out. This is why the discovery schedule is typically set such that the discovery procedure is carried out when the network load is low, i.e. during the night. However, performing the discovery at predetermined time intervals has the disadvantage that network nodes which are connected to the network only temporarily can be missed by the discovery. In particular this applies to portable computers, such as lap top computers which are frequently connected and disconnected to the network by means of a docking station.